Mites

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There are more than 250 species of mites that can cause problems for humans and domestic animals. There are many types of problems that these can cause, such as; temporary irritation of the skin due to bites, persistent dermatitis due to mites invading skin or hair follicles, mite-induced allergies, transmission of pathogenic microbial agents, intermediate host of tapeworms, invading respiratory passages, ear canals and internal organs, fear of mites called acarophobia, or delusory acariosis, convinced infestation of oneself by mites when none are present.

Description:

Mites are closely related to ticks, they have two body segments, four legs as nymphs and adults and three legs as larvae.

Eggs are deposited externally or can be retained within the female.

The prelarva stage is a non-feeding stage that may or may not have legs or mouthparts or other distinct features.

The larva stage is an active form prior to the nymph stage. Nymphs resemble the adults but are smaller.

Mites are successful parasites that can exploit a vertebrate host very well. Mites can infest skin, scales, feathers or fur of the host and sometimes enter the body cavity, respiratory passages or internal tissues and organs.

Mites of importance:

The chicken mite, Dermanyssus gallinae, causes dermatitis in avian hosts and domestic mammals (horses, dogs, cats, cattle, rodents, rabbits and others). Severe infestations can occur and cause economic losses in domestic chicken. The chicken mite will hide in crevices during the day and emerge at night to feed on birds.

Cattle follicle mites, Demodex bovis, infest the hair follicle of cattle. A population of 100 to 1000 mites per follicle can occur and will form dermal papules or cysts. The mites can be felt by the host but are difficult to see. The female will move to another follicle or host during mating.

The goat follicle mite, Demodex caprae, leads to the development of dermal papules and nodules on the face, neck, axillary region, or udder. The goat follicle mite can infest young and pregnant does and dairy goats causing caprine demodicosis. Goat follicle mites are transferred to newborns by parental licking.

The sheep itch mite, Psorobia ovis, infests all breeds of domestic sheep. Spread of this mite through a flock is slow and occurs most often during the winter months.

The scabies mite, Sarcoptes scabiei, infests all domestic animals, except cats and guinea pigs and is indistinguishable from the human scabies mites. All the developmental stages live in burrows formed by the adult female. Detecting mites and burrows in infected animals is very difficult; infection is determined by the clinical signs. The chances of having an outbreak are more common in the winter months and are transmitted by direct contact.

The sheep scab mite, Psoroptes ovis, causes psoroptic mange in sheep and cattle and occurs in the more densely haired or wooly parts of sheep. Infestations are accompanied with heavy crusting, scab formations with inflammation, and hair damage. Many times the damage is self-inflicted by extensive licking, biting, and rubbing.

The chorioptic scab mites, Chorioptes bovis which infest cattle, occur primarily on the legs and feet of the host. Most animals do not show signs of infestation or discomfort, even at high densities. Most cattle and sheep that are infested do no show symptoms and become silent carriers to other animals. Extensive mange and pruritus can occur when mite numbers reach into the thousands.

The psoroptic ear mite, Psoroptes cuniculi, is found infesting sheep and can cause varying degrees of problems. In older animals, infestations can lead to inflammation of the ears, hematomas and suppurating abscesses. Prevalence rate of this mite is high in the US at 80-90%.

The cattle ear mite, Raillietia auris, infests dairy and beef cattle in the US but is relatively harmless. These mites can cause blockage of the auditory canal with paste-like wax plugs.

Animals Attacked:

Most vertebrates and humans

Veterinary Impact:

Mites are vectors of many disease agents and can cause mite-induced dermatitis. Mites can also cause irritation when they bite.

Mites of importance:

The chicken mite causes papules on any part of the bird. Heavy infestations can be debilitating and result in skin irritation, stunted growth, loss of vigor, reduced egg production, anemia and even death.

The cattle follicle mite causes lesions on the neck, shoulders and axillary region and sometimes the udder. Papulonodular demodicosis can occur in pregnant or lactating cows. Nodules will form over time and will range in size from a pin head to a chicken egg. These nodules can rupture and produce sores; skin damage from these sores can lead to defects in raw leather and economic losses in the tanning industry.

The goat follicle mite forms nodules up to 4 cm in diameter in the skin, certain breeds are more sensitive.

The sheep itch mite causes dry scruffy skin, loss of hair, and erythema at times. Infested sheep become restless and will bite or rub the affected area; this will damage the skin and the wool. Lesions caused by the sheep itch mite will frequently occur on the neck and shoulders of the animal and spread to the face, flanks, thighs, and other parts of the body.

The scabies mite causes adverse effects to the host by depositing feces into the burrows they live in; this usually occurs three weeks after the initial infestation. The infestations generally appear as papules, puritus and hair loss; then as the infestation progresses, the skin becomes thickened crusted and secondary infection occurs. In extreme infestations, sensitive animals may experience weight loss, eating difficulty, hearing impairment, blindness, exhaustion and death.

The sheep scab mites cause lesions on major portions of the body leading to extensive wool loss and weight loss; extreme cases lead to death of sheep. Cattle can develop dermatitis and hair loss that is similar to that of sheep. The infested animals can experience reduced weight gain, reduced energy conversion rates and even high maintenance energy requirements.

The chorioptic scab mite causes irritation in sensitive animals and can lead to feet stamping, rubbing and chewing of the legs, and other self-inflicted injury. In severe cases, body lesions are characterized by dermal crusting, erytherma and hair loss.

The psoroptic ear mite causes scaling, crusting, inflammation, and hair loss of the ear, as well as accumulation of wax, ear scratching, head shaking and rubbing of the head and ears. Chronic infestations can lead to anemia and weight loss and extreme cases can be fatal.

Mites have been found to be the intermediate host of tapeworms that infest domestic animals such as cattle, sheep and goats. Young animals are more susceptible than older animals to the tapeworms. Typically little harm is apparent to the host but sometimes weight loss, unthriftiness, colic and intestinal blockage will occur. Cattle and horses do not experience significant health problems but sheep do have adverse affects.

Control:

A confirmed infestation of an animal with sarcoptic and psoroptic mites requires quarantine and proper control measures. These are considered federally reportable diseases in cattle throughout the US and chorioptic mites are reportable in some states. Infestations must be reported immediately and chemicals and methods for application have regulations that must be followed in order to be used.

The approved methods of application for beef cattle and nonlactating dairy cattle include dipping the animal or using a spray-dip machine with approved acaricides, such as amitraz, coumaphos, permethrin, or phosmet, or by injection with ivermectin. Lactating dairy cattle can be treated by spraying with permethrin or coumaphos and with pour-on applications of moxidectin or eprinomectin.

To prevent an infestation, the following practices should be followed: be cautious when purchasing or boarding new animals, avoid an animal showing visible skin lesions or itchiness, isolate new acquired animals from the rest of the herd for several weeks, in feedlot operations treat all new animals with chemical when brought in, clean stalls between animals and put in new bedding, disinfect grooming tools and other instruments that are used on animals, keep animals healthy and well nourished, if any signs of itchiness or lesions develop call a veterinarian right away to check the herd.

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